Date: Sat, 5 Nov 2005 08:22:49 GMT From: Brad Huntting <huntting@glarp.com> To: freebsd-gnats-submit@FreeBSD.org Subject: kern/88518: cannot mount root rw at boot Message-ID: <200511050822.jA58MnDR096279@www.freebsd.org> Resent-Message-ID: <200511050830.jA58UFhG017840@freefall.freebsd.org>
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>Number: 88518
>Category: kern
>Synopsis: cannot mount root rw at boot
>Confidential: no
>Severity: serious
>Priority: medium
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Sat Nov 05 08:30:14 GMT 2005
>Closed-Date:
>Last-Modified:
>Originator: Brad Huntting
>Release: 6.0-RELEASE
>Organization:
>Environment:
?
>Description:
The machine in question has problems booting the 6.0-RELEASE 'boot-only' CD. But it can boot diskless over the network.
The procedure listed below works when installing 5.4-RELEASE, but not on 6.0-RELEASE. The problem is that the kernel is mounting the root partition readonly even when the root partition is an 'md' pseudo-device.
A hack in 5.4's kern/vfs_mount.c causes mountroot to use RW when mounting an md device. This appears to be missing in 6.0.
But what's more disturbing, is that the kernel flag (was it -w ?) for 'mount the root partition readwrite' appears to be missing in 5.4 and probably 6.0. This was a very usefull flag, did it change? Why was it removed?
>How-To-Repeat:
Copy the 'boot-only' cd to a tftp- and nfs-exported directory and setup dhcp.conf accordingly. For example:
filename "/scratch/diskless/FreeBSD/6.0R/boot/pxeboot";
option root-path "pernicious.glarp.com:/scratch/diskless/FreeBSD/6.0R";
Assuming you have permissions set correctly in /etc/exports, and tftp enabled from /etc/inetd.conf, a machine which net-boot's should get thrown into the FreeBSD install procedure.
>Fix:
Either restore the -w flag (or make a kernel environment switch 'boot_readwrite'), or reinstitute the hack in vfs_mount.c that causes 'md' root filesystems to be mounted readwrite initially.
>Release-Note:
>Audit-Trail:
>Unformatted:
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